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SCP Between Remote1 and Remote2 (Remote2 behind proxy)
# SCP Protip: Ever needed to copy something between two remote
# servers with a proxy (like orbital) in between them? In one step (kinda?)?
# Try using this insane `scp` invocation to copy a file from remote host 1 to remote host 2
# which is behind a proxy gateway!
scp -v -3 -o "ProxyCommand ssh -A -o StrictHostKeyChecking=no
-o UserKnownHostsFile=/dev/null proxy_user@proxyhost nc remotehost2 port_for_remotehost_2"
-o "ForwardAgent=yes" -o "StrictHostKeyChecking=no"
-o "UserKnownHostsFile=/dev/null"
user1@remotehost1:/file/1
user2@remotehost2:/file/1```
# The secret here is the -3 command. When you use the proxy command,
# the first thing `scp` does is call the proxy command (in this case
# our proxy command is ssh-ing into orbital) (we're invoking these ssh
# parameters with the -o flag). If that happens first, you'll be in a
# different network, so your remote host 1
# may not necessarily be accessible at the same IP as it would be in your
# proxy. The `-3` flag copies the file directly from your remote to the host,
# and then does all the other insanity you want it to do before it copies to
# your remote (`-3` is a kinda new flag). It's important to set you
# `UserKnownHostsFile` to `/dev/null`, lest you upset ssh by having it be concerned
# that the host names change between different legs of this `scp` operation.
# Same with setting `StrictHostKeyChecking` to `no`. We make sure we forward our
# agents as well, just to make sure everyone has everything they need to make sure
# that this file is copied successfully and comfortable
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